eap Mailing List: Re: Proposed Resolution to Issue 357: Channel Binding Definition

[Yoshihiro Ohba (yohba]

On Wed, Jun 07, 2006 at 12:56:53PM -0700, Bernard Aboba wrote:
> 
> >> The text mentions authenticator identifiers and properties, which
> >> presumably were agreed upon by the authenticator that sent them (unless
> >> it's a forgery).
> >
> >Then I think this presumption should be explicitly described in the
> >draft.
> 
> Do you want to suggest text?

How about:

" 
It is expected that the parameters are also agreed upon by the peer
and authenticator via the lower layer if the authenticator is the
valid entity that advertised the parameters.
"

> 
> >> "A secure mechanism for ensuring that a subset of the parameters
> >> transmitted by the authenticator (such as authenticator identifiers and
> >> properties) are agreed upon by the EAP peer and server."
> >
> >Transmitted to whom?  I think not all parameters do not need to be
> >transmitted to the server while all parameters need to be transmitted
> >to the peer.
> 
> I was leaving it open.   Some things might be transmitted to the peer but 
> not the server, or vice versa.  For example, the authenticator may send 
> Calling-Station-Id to the AAA server, but it doesn't send it to the peer 
> (the peer includes that in the source address).
> 
> >In fact, if the server has the pre-established knowledge
> >about the parameters, the only information that needs to be sent from
> >authenticator to the server is authenticator identity which can be
> >used as the primary database look-up key to find out other parameters
> >associated with the authenticator identity.
> 
> How can the peer use channel binding parameters which it never received?  
> So the authenticator needed to send it to the peer at least, no?

This was discussed before.  My comment was that if the authenticator
needs to advertise the channel binding parameters.

> 
> >Also I don't understand why peer's lower layer parameter such as
> >Calling-Station-Id needs to be agreed by peer and server.  What is the
> >actual threat without agreement?
> 
> The threat is that the authenticator could lie about the 
> Calling-Station-Id. The peer could then find out from the server that it 
>  got different information.
> 

The peer may be lying in this case, but the server will never know
whether authenticator or peer is lying unless the server is
preconfigured with the peer's Calling-Station-Id.

Yoshihiro Ohba